I'm Andy Warren, currently a SQL Server trainer with End to End Training. Over the past few years I've been a developer, DBA, and IT Director. I was one of the original founders of SQLServerCentral.com and helped grow that community from zero to about 300k members before deciding to move on to other ventures.

Not all of us work at companies big enough to justify the expense/time it takes to implement something like MS Mom, Altiris, etc. For years I've recommended Servers Alive as a reasonably priced (about $200) solution that lets you do basic fault monitoring. It can alert on low disk space, check that a web page is running, login to a SQL Server (which isn't the same as saying the service is running!), and notify you via email, pager, or instant message when a problem is detected. You can monitor up to 10 items for free, after that you have to pay. Most of us in the DBA world use SQL Agent to do a lot of our monitoring/alerting, but on rare occasion SQL Agent can fail. It's nice to have a secondary level of monitoring running from a different machine.

There are probably similar products out there, it's one of those "I could write that!" type apps, and I stopped looking when I found something that met my needs.